Three readings, and this is the one learners miss. 圈 is a circle, 圈 is the pen an animal lives in, and 圈 is the act of shutting it in there. The last two differ only by tone.
usage
Takes a 把 object or a location phrase: 把鸡圈起来, 圈在院子里. Used of people it is pointedly negative, closer to "cooped up" than "kept".
Outer enclosure radical (wéi) - the indexing radical, wrapping the phonetic on top, left, and bottom. The square frame visually depicts a closed boundary, supplying the 'ring / enclosed area' meaning. Same wrapping pattern in 国 (country), 园 (garden), 围 (surround).
Inner 卷 supplies the sound - juǎn drifted to quān through palatal shift, but both trace to the same Old Chinese velar series. The 'roll / curl' meaning also resonates: a circle is something curled into a closed loop. Same phonetic in 倦 (tired).
